We have a the GSG-5 rifle. It is one of the most fun to shoot firearms we have, and the wifey and I both enjoy shooting it. From my experience and what I've read, it seems like most people have good luck with the Federal 550 bulk pack that you can get at Wally World for about $14 or so. Definitely try that stuff out on your new acquisition.

Saw one of the GSG things at a local shop. Not into the whole "tactical" thing so I didn't have enough interst to handle it. MP5 look-a-like in .22lr ooooo and the fake suppressor. Didn't even see the price. I guess it's something ppl will want but whine about the cost (can't have your cake...)
At least there'll be one there for someone else with me passing on them.